In a four-wheel-drive (4WD) vehicle drivetrain, how many gearboxes are typically used (counting the main transmission and the separate transfer case)?

Introduction / Context:
A 4WD drivetrain must split torque between front and rear axles. This requires more than a single gearbox. The question probes understanding of the components that provide speed ratios and torque distribution in a typical 4WD layout.

Given Data / Assumptions:

• Conventional longitudinal engine and 4WD layout.
• Driver-selectable or full-time 4WD via a transfer case.
• Counting distinct torque-processing housings.

Concept / Approach:
The main gearbox (transmission) provides multiple speed ratios for the vehicle. A separate transfer case (often called a secondary gearbox) splits power to front and rear propeller shafts and may provide high/low ranges. Together, these are commonly described as two gearboxes in 4WD systems.

Step-by-Step Solution:

Verification / Alternative check:
Service manuals and parts diagrams list both a transmission and a transfer case as separate assemblies, each with its own housing, shafts, and gears—confirming two gearboxes in standard 4WD layouts.

Why Other Options Are Wrong:

• 1: Ignores the transfer case.
• 3 or 4: Overcounts; differentials are not classified as gearboxes.

Common Pitfalls:

• Confusing differentials (front/rear) with gearboxes. Differentials manage wheel speed differences, not driving ranges.
• Assuming AWD crossovers without a separate low range; many still have a power take-off/transfer unit distinct from the transmission.

Final Answer:
2